TM 1002:2010

Determination of the joint yield of a polyurethane foam canister

Final version: 13/01/2010

Background and purpose:

The yield of canister PU-foam is often an important point for customers buying the product. Information on labels concerning yield are often derived from laboratory tests that were done under ideal circumstances, i.e. circumstances to get the highest possible yield. Purpose of this test procedure is to determine a realistic reachable foam yield of a PU-foam canister when it is used in joints. The value will be reported in meters for a standard joint of 20x50 mm².

Apparatus and material:

• 2 pieces of plaster board of 500 mm x 100 mm x 12,5 mm (length x height x width)
• 2 polyethylene spacers of 100 mm x 30 mm x 30 mm
• A joint of 500 mm x 100 mm x 55 mm
• Water permeable paper, e.g. A3 type writer paper (80g/m2)
• Weighing scale with 0,1 g accuracy

See also Figures 1-3.

Procedure:

1. Preparation
   

   • Acclimatise test canister, plaster board and paper at 23 °C and 50 % RH for at least 24 hours.
   • Build a horizontal straight up placed joint having a width of 30 mm, depth of 100 mm and a length of 500 mm, with the plaster boards at the sides.
   • Take the typewriter paper and draw orientation lines to indicate a 40 mm height of the joint (see Figure 1). Putting the paper in the joint should give the test apparatus as in Figure 2.

   
   

2. Test description
   

   • Mount the dispenser tools (straw or gun).
   • Note the initial canister weight (m_i).
   • Don’t pre-moisten the joint.
   • Shake the can. Spray the first 50 – 100g of the can in a garbage bag and weigh the canister again (m_o).
   • Fill the joint in a way the cured foam just fills the joint and not expels out of the joint (see Figure 3). As guideline for a handheld foam fill up to ca. 40 % (4 cm) and for a gun foam fill up to ca. 80% (8 cm). The finally cured foam should fill the joint between 80 and 100%. If the cured foam does expel out of the joint or if the cured foam fills the joint less then 80%, the test should be repeated using an adapted filling level.
   • Weigh the canister again (m_n).
   • Let the foam cure for at least 24 hours at 23 °C and 50 % RH.
   • Determine the volume (V_f) of the foam piece including the paper, e. g. with Archimedes method or by water displacement see OCF TM 1007 (in this case, don’t cut the foam into pieces)
   • Repeat the procedure (steps 3 – 8) - if possible - two times with the 2^nd and 3^rd third of the can content. For both new tests one should get new figures for m_o, m_n and V_f.
   • Spray the canister empty (until spitting) and note the weight of the empty canister (m_e).
     
     
     

     Figure 1: Typewriter paper insert with orientation lines
     
     
     
     Figure 2: Build joint
     
     
     
     Figure 3: Joint with cured foam
     
     
     

   
   

3. Calculation
   
   The joint yield has to be expressed in meter length for a standard joint of 20 mm width and 50 mm depth. This “longitudinal” yield can be calculated using next equation:
   
   
   
   
   in which:
   
   Y(m)_{20x50 mm2 joint} = yield in running meters for a joint size of 20x50 mm2
   m_i = initial canister weight, expressed in grams [g]
   m_e = emptied canister weight, expressed in grams [g]
   m_o = canister weight just before joint filling, expressed in grams [g]
   m_n = canister weight just after joint filling, expressed in grams [g]
   V_f = volume of the foam piece [l]

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